Antimicrobial cationic peptides

ABSTRACT

A novel class of cationic peptides having antimicrobial activity is provided. Examples of such peptides include NH 2  -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:1) and NH 2  -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (SEQ ID NO:2).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to antimicrobial peptides and specifically to a new class of antimicrobial cationic peptides referred to as bactolysins.

2. Description of Related Art

In 1981, the self-promoted uptake hypothesis was first proposed to explain the mechanism of action of polycationic antibiotics in Pseudomonas aeruginosa. According to this hypothesis, polycations interact with sites on the outer membranes of Gram-negative bacteria at which divalent cations cross-bridge adjacent lipopolysaccharide molecules. Due to their higher affinity for these sites, polycations displace the divalent cations and, since the polycations are bulkier than the divalent cations, cause structural perturbations in the outer membrane. These perturbations result in increased outer membrane permeability to compounds such as the β-lactam antibiotic nitrocefin, the eukaryotic non-specific defense protein lysozyme and to hydrophobic substances. By analogy, molecules accessing this pathway are proposed to promote their own uptake.

It has been clearly demonstrated that the outer membranes of Gram-negative bacteria are semipermeable molecular "sieves" which restrict access of antibiotics and host defense molecules to their targets within the bacterial cell. Thus, cations and polycations which access the self-promoted uptake system are, by virtue of their ability to interact with and break down the outer membrane permeability barrier, capable of increasing the susceptibility of Gram-negative pathogenic bacteria to antibiotics and host defense molecules. Hancock and Wong demonstrated that a broad range of such compounds could overcome the permeability barrier and coined the name "permeabilizers" to describe them (Hancock and Wong, Antimicrob. Agents Chemother., 26:48, 1984). While self-promoted uptake and permeabilizers were first described for P. aeruginosa, they have now been described for a variety of Gram-negative bacteria.

Over the past decade, non-specific defense molecules have been described in many animals, including insects and humans. One subset of these molecules have in common the following features: (a) they are small peptides, usually 15-35 amino acids in length, (b) they contain 4 or more positively charged amino acid residues, either lysines or arginines, and (c) they are found in high abundance in the organisms from which they derive. Several of these molecules have been isolated, amino acid sequenced and described in the patent literature (e.g., cecropins: WO8900199, WO 8805826, WO8604356, WO 8805826; defensins: EP 193351, EP 85250, EP 162161, U.S. Pat. No. 4,659,692, WO 8911291). However, only limited amounts of these peptides can be isolated from the host species. For example, Sawyer, et al., (Infect. Immun. 56:693, 1988) isolated 100-200 mg of rabbit neutrophil defensins 1 and 2 from 10⁹ primed peritoneal neutrophils or lipopolysaccharide-elicited alveolar macrophages (i.e., the numbers present in a whole animal).

The gene for human defensin has been cloned and sequenced, but no successful expression has been demonstrated, as yet. Furthermore, production of these peptides using peptide synthesis technology produces peptides in limited amounts and is expensive when scaled up or when many variant peptides must be produced. Also, structural analysis is difficult without specific incorporation of ¹⁵ N and ¹³ C tagged amino acids which is prohibitively expensive using amino acid synthesis technology.

There is a need to develop polypeptides having a broad range of potent antimicrobial activity against a plurality of microorganisms, including gram negative bacteria, gram positive bacteria, fungi, protozoa, viruses and the like.

SUMMARY OF THE INVENTION

The present invention provides a novel class of cationic peptides, referred to as bactolysins, which have antimicrobial activity. Two representative peptides are provided and include

MBI 29, NH₂ -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:1) and

MBI 26, NH₂ -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (SEQ ID NO:2), analogs, derivatives and conservative variations thereof.

The invention also provides a method of inhibiting the growth of bacteria comprising contacting the bacteria with an inhibiting effective amount of a peptide having an amino acid sequence of MBI 29 (SEQ ID NO:1) or MBI 26 (SEQ ID NO:2) alone, or in combination with an antibiotic.

In another embodiment, the invention provides a method of inhibiting an endotoxemia or sepsis associated disorder in a subject having or at risk of having such a disorder, comprising administering to the subject a therapeutically effective amount of a peptide of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a three-dimensional schematic representation of the conformational structure of CEME, MBI 29, and MBI 26.

FIG. 2 shows the axial projection of the α-helical conformation of each peptide in 2D.

FIG. 3a shows tumor necrosis factor (TNF) levels measured 6 hours after the addition of E. coli 0111:B4 LPS and CEME (ME), CEMA (MA), and MBI 29 to macrophage cells. The data is from two separate assays.

FIGS. 3b and 3c show tumor necrosis factor (TNF) levels measured 6 hours after the addition of E. coli Bort LPS and E. coli 0111:B4 LPS and MBI 29 to macrophage cells. The data is from two separate assays.

FIG. 4 shows tumor necrosis factor (TNF) levels measured 6 hours after the addition of E. coli Bort LPS and CEME (ME), CEMA (MA) and MBI 29 to macrophage cells. The data is from two separate assays.

FIGS. 5a and 5b show RAW cell TNF production after addition of E. coli 0111:B4 LPS and the effect of the addition of MBI 29 and polymyxin B on TNF.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel classs of cationic peptides, called bactolysins, which have antimicrobial activity and have the ability to significantly reduce the level of lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF). These peptides are useful for inhibiting microbial infection or growth, as well reducing the effects of endotoxemia and are often synergistic with conventional antibiotics and/or lysozyme. In addition, such peptides are useful as antifungal agents, antitumor agents, or antiviral agents.

The term "antimicrobial" as used herein means that the peptides of the present invention inhibit, prevent, or destroy the growth or proliferation of microbes such as bacteria, fungi, viruses or the like. The term "antiviral" as used herein means that the peptides of the present invention inhibit, prevent or destrroy the growth or proliferation of viruses or of virally-infected cells. The term "anti-tumor" as used herein means that the peptides of the present invention may be used to inhibit the growth of or destroy tumors. The term "antifungal" as used herein means that the peptides of the present inventon may be used to inhibt the growth of or destroy fungi.

In a first embodiment, the invention provides an isolated antimicrobial peptide having an amino acid sequence:

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VLTTGLPALIS-COOH (SEQ ID NO:7),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VVTTAKPLISS-COOH (SEQ ID NO:8),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ ILTTGLPALIS-COOH (SEQ ID NO:9),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GGLLSNIVTSL-COOH (SEQ ID NO:10), or

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GPILANLVSIV-COOH (SEQ ID NO:11)

wherein R₁ is a hydrophobic amino acid residue and R₂ is a hydrophilic amino acid residue.

Examples of such peptides of the invention include but are not limited to:

NH₂ -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (MBI 29) (SEQ ID NO:1),

NH₂ -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (MBI 26) (SEQ ID NO:2),

NH₂ -KWKSFIKNLTKGGSKILTTGLPALIS-COOH (MBI 201) (SEQ ID NO:3),

NH₂ -KWKKFIKNLTKGGSKILTTGLPALIS-COOH (MBI 202) (SEQ ID NO:4),

NH₂ -KWKSFIKNLEKVLKPGGLLSNIVTSL-COOH (MBI 203) (SEQ ID NO:5), and

NH₂ -KWKSFIKNLEKVLKKGPILANLVSIV-COOH (MBI 204) (SEQ ID NO:6),

analogs, derivatives and conservative variations thereof, wherein the peptides have antimicrobial activity. The peptides of the invention include SEQ ID NO:1-6, as well as the broader groups of peptides having hydrophilic and hydrophobic substitutions, and conservative variations thereof.

The sequence of SEQ ID NO:1 contains helix-forming hydrophilic amino acids at residues 4, 8, 10, 11, and 14. Amino acids 6 and 9 are hydrophobic residues (see FIG. 1). The helical nature of the first 10 amino acids is depicted in FIGS. 1 and 2. The cationic charge of the peptide of SEQ ID NO:1 was achieved by placing a lysine at positions 8 and 14, thereby increasing the total positive charge to 6. The carboxy terminus of SEQ ID NO:1 was converted to the methyl ester and the antibacterial activity of this derivative was the same as that of the unmodified peptide. The peptide of SEQ ID NO:1 also has antifungal activity. Amino acid residues 3, 4, 7, 8, 10, 11, 14, and 15 are preferably hydrophilic residues, while amino acid residues 2, 5, 6, 9, 12, and 13 are preferably hydrophobic residues.

SEQ ID NO:1 was modified to increase the alpha helical nature by changing amino acids in the C-terminal tail, thereby resulting in SEQ ID NO:2. Amino acids 11 (neutral hydrophilic) and 13 (hydrophobic) of SEQ ID NO:1 were changed to another neutral hydrophilic and hydrophobic amino acid, respectively, in order to increase alpha helicity in this region. The C-terminal tail (residue 20-26) was modified to include a positive charge and increase alpha helicity. Therefore residues 20, 21, 23, 24 and 25 were changed (See FIGS. 1 and 2). SEQ ID NO:3 was obtained by changing amino acids 8, 11, 12, 13, 14, and 16 of SEQ ID NO:1. The first 15 amino acid residues contain lysine at every fourth residue of the alpha helix. Thus, the lysines at positions 8 and 14 in SEQ ID NO:1 were replaced by asparagine and serine, respectively, and the serine at position 11 was changed to lysine. Further changes were made at positions 12, 13 and 16 to conserve the helical nature. The C-terminal tail was unchanged. SEQ ID NO:4 is identical to SEQ ID NO:3, except for the amino acid at position 4, which incorporates an additional positive charge. SEQ ID NO:5 and SEQ ID NO:6 represent peptides having the same amino acid sequence as SEQ ID NO:3 for the first 9 amino acids. The amino acid at position 10 is glutamic acid. Residues 10, 11, 12, and 13 in both SEQ ID NO:5 and SEQ ID NO:6 are different than SEQ ID NO:1, but remain either hydrophilic or hydrophobic as described above.

Residue 14 in SEQ ID NO:5 is the same as in SEQ ID NO:1. All residues thereafter, 15-26, are completely changed to construct a hydrophobic helical tail, and bears no resemblance to the tail of SEQ ID NO:1. SEQ ID NO:6 contains the same residues as SEQ ID NO:1 at positions 14 and 15. Residues 16-26 have been changed to form a helical tail.

The term "isolated" as used herein refers to a peptide substantially free of proteins, lipids, nucleic acids, for example, with which it is naturally associated. Those of skill in the art can make similar substitutions to achieve peptides with greater antibacterial activity and a broader host range. For example, the invention includes the bactolysin peptides depicted in SEQ ID NO:1-6, as well as analogues or derivatives thereof, as long as the bioactivity of the peptide remains. Minor modifications of the primary amino acid sequence of the peptides of the invention may result in peptides which have substantially equivalent activity as compared to the specific peptides described herein. Such modifications may be deliberate, as by site-directed mutagenesis, or may be spontaneous. All of the peptides produced by these modifications are included herein as long as the biological activity of the original peptide still exists.

Further, deletion of one or more amino acids can also result in a modification of the structure of the resultant molecule without significantly altering its biological activity. This can lead to the development of a smaller active molecule which would also have utility. For example, amino or carboxy terminal amino acids which may not be required for biological activity of the particular peptide can be removed. Peptides of the invention include any analog, homolog, mutant, isomer or derivative of the peptides disclosed in the present invention, so long as the bioactivity as described herein is remains. All peptides were synthesized using L amino acids, however, all D forms of the peptides (e.g., see Table 1B, CEMA) can be synthetically produced. In addition, C-terminal derivatives can be produced, such as C-terminal methyl esters, in order to increase the antimicrobial activity of a peptide of the invention.

The peptide of the invention include peptides which are conservative variations of those peptides specifically exemplified herein. The term "conservative variation" as used herein denotes the replacement of an amino acid residue by another, biologically similar residue. Examples of conservative variations include the substitution of one hydrophobic residue such as isoleucine, valine, leucine, alanine, cysteine, glycine, phenylalanine, proline, tryptophan, tyrosine, norleucine or methionine for another, or the substitution of one polar residue for another, such as the substitution of arginine for lysine, glutamic for aspartic acids, or glutamine for asparagine, and the like. Neutral hydrophilic amino acids which can be substitued for one another include asparagine, glutamine, serine and threonine. The term "conservative variation" also includes the use of a substituted amino acid in place of an unsubstituted parent amino acid provided that antibodies raised to the substituted polypeptide also immunoreact with the unsubstituted polypeptide. Such conservative substitutions are within the definition of the classes of the peptides of the invention with respect to R₁ and R₂.

The biological activity of the peptides can be determined by standard methods known to those of skill in the art, such as "minimal inhibitory concentration (MIC)" assay described in the present examples, whereby the lowest concentration at which no change in OD is observed for a given period of time is recorded as MIC. Alternatively, "fractional inhibitory concentration (FIC)" is also useful for determination of synergy between the peptides of the invention, or the peptides in combination with known antibiotics. FICs are performed by checkerboard titrations of peptides in one dimension of a microtiter plate, and of antibiotics in the other dimension, for example. The FIC is calculated by looking at the impact of one antibiotic on the MIC of the other and vice versa. An FIC of one indicates that the influence of the compounds is additive and an FIC of less than one indicates synergy.

Peptides of the invention can be synthesized by such commonly used methods as t-BOC or FMOC protection of alpha-amino groups. Both methods involve stepwise syntheses whereby a single amino acid is added at each step starting from the C terminus of the peptide (See, Coligan, et al., Current Protocols in Immunology, Wiley Interscience, 1991, Unit 9). Peptides of the invention can also be synthesized by the well known solid phase peptide synthesis methods described Merrifield, J. Am. Chem. Soc., 85:2149, 1962), and Stewart and Young, Solid Phase Peptides Synthesis, (Freeman, San Francisco, 1969, pp.27-62), using a copoly(styrene-divinylbenzene) containing 0.1-1.0 mMol amines/g polymer. On completion of chemical synthesis, the peptides can be deprotected and cleaved from the polymer by treatment with liquid HF-10% anisole for about 1/4-1 hours at 0° C. After evaporation of the reagents, the peptides are extracted from the polymer with 1% acetic acid solution which is then lyophilized to yield the crude material. This can normally be purified by such techniques as gel filtration on Sephadex G-15 using 5% acetic acid as a solvent. Lyophilization of appropriate fractions of the column will yield the homogeneous peptide or peptide derivatives, which can then be characterized by such standard techniques as amino acid analysis, thin layer chromatography, high performance liquid chromatography, ultraviolet absorption spectroscopy, molar rotation, solubility, and quantitated by the solid phase Edman degradation.

The invention includes polynucleotides encoding:

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VLTTGLPALIS-COOH (SEQ ID NO:7),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VVTTAKPLISS-COOH (SEQ ID NO:8),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ ILTTGLPALIS-COOH (SEQ ID NO:9),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GGLLSNIVTSL-COOH (SEQ ID NO:10), and

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GPILANLVSIV-COOH (SEQ ID NO:11)

wherein R₁ is a hydrophobic amino acid residue and R₂ is a hydrophilic amino acid residue. More specifically, the invention also includes an isolated polynucleotide which encodes the MBI 29 peptide of SEQ ID NO:1, an isolated polynucleotide which encodes the MBI 26 peptide of SEQ ID NO:2, and isolated polynucleotides which encode SEQ ID NO:3-6. In addition, the invention includes polynucleotides which encode analogs, mutants and variants of the peptides of the invention. The term "isolated" as used herein refers to a polynucleotide substantially free of proteins, lipids, nucleic acids, for example, with which it is naturally associated. As used herein, "polynucleotide" refers to a polymer of deoxyribonucleotides or ribonucleotides, in the form of a separate fragment or as a component of a larger construct. DNA encoding a peptide of the invention can be assembled from cDNA fragments or from oligonucleotides which provide a synthetic gene which is capable of being expressed in a recombinant transcriptional unit. Polynucleotide sequences of the invention include DNA, RNA and cDNA sequences. A polynucleotide sequence can be deduced from the genetic code, however, the degeneracy of the code must be taken into account. Polynucleotides of the invention include sequences which are degenerate as a result of the genetic code. Such polynucleotides are useful for the recombinant production of large quantities of a peptide of interest, such as the peptide of SEQ ID NO:1, 2, 3, 4, 5, and 6.

In the present invention, the polynucleotides encoding the cationic peptides of the invention may be inserted into a recombinant "expression vector". The term "expression vector" refers to a plasmid, virus or other vehicle known in the art that has been manipulated by insertion or incorporation of cationic genetic sequences. Such expression vectors of the invention are preferably plasmids which contain a promoter sequence which facilitates the efficient transcription of the inserted genetic sequence in the host. The expression vector typically contains an origin of replication, a promoter, as well as specific genes which allow phenotypic selection of the transformed cells. For example, the expression of the peptides of the invention can be placed under control of E. coli chromosomal DNA comprising a lactose or lac operon which mediates lactose utilization by elaborating the enzyme beta-galactosidase. The lac control system can be induced by IPTG. A plasmid can be constructed to contain the lac Iq repressor gene, permitting repression of the lac promoter until IPTG is added. Other promoter systems known in the art include beta lactamase, lambda promoters, the protein A promoter, and the tryptophan promoter systems. While these are the most commonly used, other microbial promoters, both inducible and constitutive, can be utilized as well. The vector contains a replicon site and control sequences which are derived from species compatible with the host cell. In addition, the vector may carry specific gene(s) which are capable of providing phenotypic selection in transformed cells. For example, the beta-lactamase gene confers ampicillin resistance to those transformed cells containing the vector with the beta-lactamase gene.

Transformation of a host cell with the polynucleotide may be carried out by conventional techniques well known to those skilled in the art. For example, where the host is prokaryotic, such as E. coli, competent cells which are capable of DNA uptake can be prepared from cells harvested after exponential growth and subsequently treated by the CaCl₂ method using procedures well known in the art. Alternatively, MgCl₂ or RbCl could be used.

In addition to conventional chemical methods of transformation, the plasmid vectors of the invention may be introduced into a host cell by physical means, such as by electroporation or microinjection. Electroporation allows transfer of the vector by high voltage electric impulse, which creates pores in the plasma membrane of the host and is performed according to methods well known in the art. Additionally, cloned DNA can be introduced into host cells by protoplast fusion, using methods well known in the art.

DNA sequences encoding the cationic peptides can be expressed in vivo by DNA transfer into a suitable host cell. "Host cells" of the invention are those in which a vector can be propagated and its DNA expressed. The term also includes any progeny of the subject host cell. It is understood that not all-progeny are identical to the parental cell, since there may be mutations that occur during replication. However, such progeny are included when the terms above are used. Preferred host cells of the invention include E. coli S. aureus and P. aeruginosa, although other Gram-negative and Gram-positive organisms known in the art can be utilized as long as the expression vectors contain an origin of replication to permit expression in the host.

The cationic peptide polynucleotide sequence used according to the method of the invention can be isolated from an organism or synthesized in the laboratory. Specific DNA sequences encoding the cationic peptide of interest can be obtained by: 1) isolation of a double-stranded DNA sequence from the genomic DNA; 2) chemical manufacture of a DNA sequence to provide the necessary codons for the cationic peptide of interest; and 3) in vitro synthesis of a double-stranded DNA sequence by reverse transcription of mRNA isolated from a donor cell. In the latter case, a double-stranded DNA complement of mRNA is eventually formed which is generally referred to as cDNA.

The synthesis of DNA sequences is frequently the method of choice when the entire sequence of amino acid residues of-the desired peptide product is known. In the present invention, the synthesis of a DNA sequence has the advantage of allowing the incorporation of codons which are more likely to be recognized by a bacterial host, thereby permitting high level expression without difficulties in translation. In addition, virtually any peptide can be synthesized, including those encoding natural cationic peptides, variants of the same, or synthetic peptides.

When the entire sequence of the desired peptide is not known, the direct synthesis of DNA sequences is not possible and the method of choice is the formation of cDNA sequences. Among the standard procedures for isolating cDNA sequences of interest is the formation of plasmid or phage containing cDNA libraries which are derived from reverse transcription of mRNA which is abundant in donor cells that have a high level of genetic expression. When used in combination with polymerase chain reaction technology, even rare expression products can be cloned. In those cases where significant portions of the amino acid sequence of the cationic peptide are known, the production of labeled single or double-stranded DNA or RNA probe sequences duplicating a sequence putatively present in the target cDNA may be employed in DNA/DNA hybridization procedures which are carried out on cloned copies of the cDNA which have been denatured into a single stranded form (Jay, et al., Nuc. Acid Res., 11:2325, 1983).

The invention also provides a method of inhibiting the growth of bacteria comprising contacting the bacteria with an inhibiting effective amount of a peptide of the invention, including:

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VLTTGLPALIS-COOH (SEQ ID NO:7),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ VVTTAKPLISS-COOH (SEQ ID NO:8),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ ILTTGLPALIS-COOH (SEQ ID NO:9),

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GGLLSNIVTSL-COOH (SEQ ID NO:10), or

NH₂ -KWKR₂ R₁ R₁ R₂ R₂ R₁ R₂ R₂ R₁ R₁ R₂ R₂ GPILANLVSIV-COOH (SEQ ID NO:11)

wherein R₁ is a hydrophobic amino acid residue and R₂ is a hydrophilic amino acid residue. More specifically, the invention provides a method of inhibiting the growth of bacteria comprising contacting the bacteria with an inhibiting effective amount of a peptide of the invention, such as MBI 29,

NH₂ -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:1),

NH₂ -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (SEQ ID NO:2),

NH₂ -KWKSFIKNLTKGGSKILTTGLPALIS-COOH (SEQ ID NO:3),

NH₂ -KWKKFIKNLTKGGSKILTTGLPALIS-COOH (SEQ ID NO:4),

NH₂ -KWKSFIKNLEKVLKPGGLLSNIVTSL-COOH (SEQ ID NO:5), and

NH₂ -KWKSFIKNLEKVLKKGPILANLVSIV-COOH (SEQ ID NO:6), and

analogs, derivatives, or conservative variations thereof.

The term "contacting" refers to exposing the bacteria to the peptide so that the peptide can effectively inhibit, kill, or lyse bacteria, bind endotoxin (LPS), or permeabilize gram-negative bacterial outer membranes. Contacting may be in vitro, for example by adding the peptide to a bacterial culture to test for susceptibility of the bacteria to the peptide. Contacting may be in vivo, for example administering the peptide to a subject with a bacterial disorder, such as septic shock. "Inhibiting" or "inhibiting effective amount" refers to the amount of peptide which is required to cause a bacteriostatic or bactericidal effect. Examples of bacteria which may be inhibited include E. coli, P. aeruginosa, E. cloacae, S. typhimurium, and S. aureus. The method of inhibiting the growth of bacteria may further include the addition of antibiotics for combination or synergistic therapy. The appropriate antibiotic administered will typically depend on the susceptibility of the bacteria such as whether the bacteria is gram negative or gram positive, and will be easily discernable by one of skill in the art. The peptides and/or analogues or derivatives thereof may be administered to any host, including a human or non-human animal, in an amount effective to inhibit not only growth of a bacterium, but also a virus or fungus. These peptides are useful as antimicrobial agents, antiviral agents, and antifungal agents.

The peptide of the invention can be administered parenterally by injection or by gradual infusion over time. The peptide can be administered intravenously, intraperitoneally, intramuscularly, subcutaneously, intracavity, or transdermally. Preferred methods for delivery of the peptide include orally, by encapsulation in microspheres or proteinoids, by aerosol delivery to the lungs, or transdermally by iontophoresis or transdermal electroporation. Other methods of administration will be known to those skilled in the art.

Preparations for parenteral administration of a peptide of the invention include sterile aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic/aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer's, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer's dextrose), and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, antioxidants, chelating agents, and inert gases and the like.

The invention provides a method of treating or ameliorating an endotoxemia or septic shock (sepsis) associated disorder, or one or more of the symptoms of sepsis comprising administering to a subject displaying symptoms of sepsis or at risk for developing sepsis, a therapeutically effective amount of a cationic peptide of the invention, for example, SEQ ID NO:1, or analogs, derivatives, or conservative variations thereof. The term "ameliorate" refers to a decrease or lessening of the symptoms of the disorder being treated. Such symptoms which may be ameliorated include those associated with a transient increase in the blood level of TNF, such as fever, hypotension, neutropenia, leukopenia, thrombocytopenia, disseminated intravascular coagulation, adult respiratory distress syndrome, shock and multiple organ failure. Patients who require such treatment include those at risk for or those suffering from toxemia, such as endotoxemia resulting from a gram-negative bacterial infection, venom poisoning, or hepatic failure, for example. In addition, patients having a gram-positive bacterial, viral or fungal infection may display symptoms of sepsis and may benefit from such a therapeutic method as described herein. Those patients who are more particularly able to benefit from the method of the invention are those suffering from infection by E. coli, Haemophilus influenza B, Neisseria meningitides, staphylococci, or pneumococci. Patients at risk for sepsis include those suffering from gunshot wounds, renal or hepatic failure, trauma, burns, immunocompromised (HIV), hematopoietic neoplasias, multiple myeloma, Castleman's disease or cardiac myxoma.

The term "therapeutically effective amount" as used herein for treatment of endotoxemia refers to the amount of cationic peptide used is of sufficient quantity to decrease the subject's response to LPS and decrease the symptoms of sepsis. The term "therapeutically effective" therefore includes that the amount of cationic peptide sufficient to prevent, and preferably reduce by at least 50%, and more preferably sufficient to reduce by 90%, a clinically significant increase in the plasma level of TNF. The dosage ranges for the administration of cationic peptide are those large enough to produce the desired effect. Generally, the dosage will vary with the age, condition, sex, and extent of the infection with bacteria or other agent as described above, in the patient and can be determined by one skilled in the art. The dosage can be adjusted by the individual physician in the event of any contraindications. In any event, the effectiveness of treatment can be determined by monitoring the level of LPS and TNF in a patient. A decrease in serum LPS and TNF levels should correlate with recovery of the patient.

In addition, patients at risk for or exhibiting the symptoms of sepsis can be treated by the method as described above, further comprising administering, substantially simultaneously with the therapeutic administration of cationic peptide, an inhibitor of TNF, an antibiotic, or both. For example, intervention in the role of TNF in sepsis, either directly or indirectly, such as by use of an anti-TNF antibody and/or a TNF antagonist, can prevent or ameliorate the symptoms of sepsis. Particularly preferred is the use of an anti-TNF antibody as an active ingredient, such as a monoclonal antibody with TNF specificity as described by Tracey, et al. (Nature, 330:662, 1987).

A patient who exhibits the symptoms of sepsis may be treated with an antibiotic in addition to the treatment with cationic peptide. Typical antibiotics include an aminoglycoside, such as gentamicin or a beta-lactam such as penicillin, or cephalosporin. Therefore, a preferred therapeutic method of the invention includes administering a therapeutically effective amount of cationic peptide substantially simultaneously with administration of a bactericidal amount of an antibiotic. Preferably, administration of cationic peptide occurs within about 48 hours and preferably within about 2-8 hours, and most preferably, substantially concurrently with administration of the antibiotic.

The term "bactericidal amount" as used herein refers to an amount sufficient to achieve a bacteria-killing blood concentration in the patient receiving the treatment. The bactericidal amount of antibiotic generally recognized as safe for administration to a human is well known in the art, and as is known in the art, varies with the specific antibiotic and the type of bacterial infection being treated.

Because of the antibiotic, antimicrobial, and antiviral properties of the peptides, they may also be used as preservatives or sterillants of materials susceptible to microbial or viral contamination. The peptides of the invention can be utilized as broad spectrum antimicrobial agents directed toward various specific applications. Such applications include use of the peptides as preservatives in processed foods (organisms including Salmonella, Yersinia, Shigella), either alone or in combination with antibacterial food additives such as lysozymes; as a topical agent (Pseudomonas, Streptococcus) and to kill odor producing microbes (Micrococci). The relative effectiveness of the cationic peptides of the invention for the applications described can be readily determined by one of skill in the art by determining the sensitivity of any organism to one of the peptides.

The following examples are intended to illustrate but not limit the invention. While they are typical of those that might be used, other procedures known to those skilled in the art may alternatively be used.

EXAMPLE 1 MIC Values for Cationic Peptides

The minimum inhibitory concentrations of (MIC) of CEME, CEMA, the first 8 amino acid residues of CEME (NH₂ -KWKLFKKIGIGAVLKVLTTGLPALISCOOH; SEQ ID NO:1 with changes at residues 4, 6, 8-11, 14) and CEMA (NH₂ -KWKLFKKIGIGAVLKVLTTGLPALKLTK-COOH; SEQ NO:1 with changes at residues 4, 6, 8-11, 14, and 25-28), (Piers, K. and Hancock, R., Molec. Microbiology, 12(6), 1994) 20 carboxy terminal amino acids of melittin (MA), 8 amino terminal amino acids from cecropin, and the peptides shown in SEQ ID NO:1, MBI 29 and SEQ ID NO:2, MBI 26, were determined for a number of different bacteria (Table 1a and 1b). Briefly, cells were grown overnight at 37° C. in LB-S (Luria broth without any salt supplement) and diluted one in 10,000 in the same medium to give concentrations of about 10⁴ to 10⁵ CFU/ml. The broth dilutions were set up in a 96 well microtiter plate by putting 200 μl of LB-S containing the initial concentration of antibiotic or compound in column 1 and 100 μl of the same medium in columns 2-12. The compounds were diluted by taking 100 μl of broth from column 1 and mixing it with column 2, resulting in a one in two dilution. This was continued to column 10. Finally, 10 μl of bacteria were pipetted into columns 1-11, and the plates incubated overnight at 37° C. The next day the plates were scored for growth in the wells, and the MIC determined.

                  TABLE 1a     ______________________________________     MINIMUM INHIBITORY CONCENTRATION     (MIC) VALUES FOR CATIONIC PEPTIDES     STRAIN    CEME    CEMA    MBI 29                                     MBI 26                                           CE-8 MA-20     ______________________________________     S. aureus 32      ≧64                               20    ≧64                                           ≧64                                                ≧64     (K147)     S. aureus 24      ≧64                               18    ≧64                                           ≧64                                                ≧64     (SAP0017)     S. epidermis               16      ≧64                               10    ≧64                                           ≧64                                                ≧64     E. coli    5         10    3        3 ≧64                                                ≧64     (UB1005)     P. aeruginosa                8         26    5       11 ≧64                                                ≧64     (H187)     Candida albicans               ≧64                       ≧64                               40    ≧64                                           ≧64                                                ≧64     (CAN105)     ______________________________________

In a separate set of experiments, the following MIC values were obtained:

                  TABLE 1b     ______________________________________     MINIMUM INHIBITORY CONCENTRATION     (MIC) VALUES FOR CATIONIC PEPTIDES                               MBI   MBI   MBI   MBI     STRAIN   CEMA    CEMA.sup.me                               29    29.sup.me                                           26D   26L     ______________________________________     S. aureus              ≧64                      ≧64                               32    16    ≧64                                                 ≧64     (K147)     S. aureus              ≧64                      ≧64                               32    16    ≧64                                                 ≧64     (SAP0017)     S. epidermis                 43      43    16     8     8-16    32     P. aeruginosa                 32      53    16     8       16    32     (H187)     E. coli     13      32     4     4    4-8       4     (UB1005)     E. faecalis              ≧64                      ≧64                               32    ≧64                                           ≧64                                                 ≧64     Candida  ≧64                      ≧64                               32    32    ≧64                                                 ≧64     albicans     (CAN105)     ______________________________________

The results show that both MBI 29 (SEQ ID NO:1) and MBI 26 (SEQ ID NO:2) are effective antimicrobial agents for a variety of gram positive and gram negative bacteria. In addition, all peptides were effective against Candida albicans. Modification of the peptides, such as methyl ester modification, or L to D amino acids provided a broader class of antimicrobial agents.

EXAMPLE 2 Inhibition of LPS-Mediated TNF Induction in Macrophages by Cationic Peptides

The effect of cationic peptides, CEME (KWKLFKKIGIGAVLKVLTTGLPALIS) (SEQ ID NO:14) and CEMA (KWKLFKKIGIGAVLKVLTTGLPALKLTK) (SEQ ID NO:15) and the peptides of the invention, MBI 29, NH₂ -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:1) and MBI 26, NH₂ -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (SEQ ID NO:2), on LPS-induced TNF in macrophages was examined. RAW 264.7 macrophage cells were grown by seeding 10⁶ cells into a 162 cm² cell culture flask and incubated at 37° C., 5% CO₂ for 1 week. RAW cell media (Dulbecco's Modified Eagle Medium with Hepes buffer 450 ml; 2.4 mM L-glutamine 3 ml (400 mM); Pen/Strep 3 ml (10⁴ U/ml of Pen, 1 mg/ml strep); and 10% heat inactivated fetal bovine serum (FBS) 50 ml)! was then completely removed from flasks. 10 mls of cell dissociation solution (Sigma) was added to each flask and incubated at 37° C. for 10 minutes. Cells were removed from flasks, diluted in RAW cell media and centrifuged for 6 minutes. The cell pellet was resuspended in 5 ml of media/flask used. 100 μl cell suspension was removed and added to 400 μl of trypan blue and cells were counted using a hemocytometer. The cell suspension was diluted to 1×10⁶ cells/ml and 1 ml of suspension was added per well of a 24 well plate. The 24 well plates were incubated at 37° C., 5% CO₂ overnight for use in the assay.

After an overnight incubation, the media was aspirated from all the wells. 100 μl of Lipopolysaccharide (LPS) was added at 100 ng/100 μl. CEME, CEMA or MBI 29 was added at the desired concentration/100 μl to specified wells. RAW cell media was added to all the wells so they all had a final volume of 1 ml. The plates were then incubated for six hours at 37° C., 5% CO₂. The supernatant was then removed from the wells and stored overnight at 4° C. For those wells in which whole bacteria were added directly to the wells, the supernatant was centrifuged in 0.2 μm filter eppendorf tubes for 5 minutes.

The supernatants were then used in cell cytotoxic L929 assay. The samples were transferred to 96 well plates. 50 μl of TNF media was added to all the wells in all the plates except to those wells in the first row. 10 μl of murine TNF standard (20 ng/ml) and 90 μl of TNF media was added in duplicate to the plate and diluted 1:2 down the plate to the second to last row. Test samples (75 μl), comprising of the supernatants from the RAW cell assays, were added to separate rows in duplicate and diluted 1:3 to the second to last rows.

TNF-sensitive L929 mouse fibroblast cells were grown by seeding 10⁶ cells into a 162 cm² cell culture flask and left to grow for 1 week. L929 cells were removed from the flask with 10 mls of trypsin-EDTA/flask and incubated 3-5 minutes. Cell suspension was diluted and centrifuged for 6 minutes. The pellet was resuspended in 5 mls of fresh L929 media/flask and counted (same as RAW cells). Cell suspension was diluted to 10⁶ cells/ml. 100 μl was used to inoculate each well of the 96 well plates with the supernatants. (L929 Growth Media was the same as RAW cell media except instead of FBS, 50 mls of 10% heat inactivated horse serum was utilized; TNF Assay Media was the same as RAW cell media except 4 μg/ml Actinomycin D was added.)

The plates were incubated at 37° C. at 5% CO₂ for 2 days. The media was then aspirated and replaced with 100 μl of the dye MTT (0.5 mg/ml) in modified Eagle Medium without phenol red. The plates were then incubated at 37° C. at 5% CO₂ for 3 hours. The dye was then removed and replaced with 100 μl of absolute ethanol. The plates were left at room temperature for 10-15 minutes to dissolve the formazan dye crystals.

The plates were read at 570 nm in a ELISA plate reader with 690 nm reference filter. One unit of TNF activity is defined as the amount required to kill 50% of the L929 cells. The TNF level in Units per ml therefore was the reciprocal of the dilution which led to a 50% killing of L929 cells.

FIGS. 3 and 4 show levels of TNF (U/ml) after a 6 hour treatment with increasing amounts (0, 5, 10, 20, 30, 40 or 50 μg) of either CEME (ME), CEMA (MA) or MBI 29 (SEQ ID NO:1) peptide and 100 ng of LPS. TNF levels were measured six hours after the addition of E. coli 0111:B4 or E. coli Bort LPS (FIGS. 3a, 3b, 3c and FIG. 4 as labeled). The data shows the results of 2 separate experiments and indicate that both peptides efficiently reduce the level of LPS-induced TNF in the culture with two distinct LPS samples at concentrations of peptides as low as 5 μg/ml.

EXAMPLE 3 Cationic Peptide Reduction of LPS-Induced TNF

In order to determine how rapidly the cationic peptides reduced LPS-induced TNF production, E. coli 0111:B4 was added at time 0 to RAW macrophages. MEBI 29 or Polymyxin B was added at time 0, 30 and 60 minutes. Levels of TNF were measured after 6 hours. The results are shown in FIGS. 5a and 5b(PMB, Polymyxin B; 29, MBI 29 (SEQ ID NO:1)). The results show that MBI 29 inhibited TNF induction by LPS in a similar manner to polymyxin B. Furthermore, MBI 29 was effective at reducing the ability of LPS to induce TNF in RAW cell lines even when added 60 minutes after the addition of LPS. MBI 29 demonstrated a distinct and reproducible advantage over polymyxin B when added 60 minutes after the addition of LPS. To confirm that MBI 29 was acting on LPS rather than directly upon macrophage cell lines, 20 μg of MBI 29 was added to RAW cells and incubated for 60 minutes prior to aspiration of the medium and washing the cells 3 times with HBSS (Hanks Buffered Salt Solution). Addition of 10 ng or 100 ng of LPS to the washed RAW cells resulted in a high level of TNF induction (14,000-20,000 Units of TNF per ml), suggesting that the MBI 29 had not permanently depressed the ability of RAW cells to induce TNF in response to LPS addition. In contrast, the aspirated medium containing MBI 29 could depress the ability of fresh RAW cells to induce TNF in response to 10 n or 100 ng of E. coli LPS by 98.5% and 75% respectively. Up to 50 μg of MBI 29 caused no apparent decrease in RAW cell viability as judged by Trypan blue exclusion.

EXAMPLE 4 Protection From Lethal LPS Endotoxocity in a Mouse Endotoxic Shock Model

The ability of MBI 29 and MBI 26 to protect against LPS-induced endotoxemia is assessed in vivo. Mice (8-10 weeks old) are injected intraperitoneally with 20 μg D-galactosamine (Dgal) to sensitize them to LPS according to the method of Galanos (Galanos, et al., Proc. Natl. Acad. Sci., USA, 76:5939-5943, 1979), followed by 0, 50, 100, or 200 μg MBI 29 or MBI 26 in 100 μl. Immediately afterwards LPS (10 or 20 μg) in 100 μl is injected. The mice are observed at 24 and 48 hours after injections and survivors noted.

To demonstrate that survival is associated with a reduction in TNF levels, 10 μg of LPS and 20 mg of Dgal are injected at time 0. Thirty minutes later, the mice are sacrificed and the blood is taken and centrifuged to separate the serum which was used in the cell cytotoxic L929 assay. The results suggest that the bactolysins have potential in therapy against endotoxin-associated disorders.

Although the invention has been described with reference to the presently preferred embodiment, it should be understood that various modifications can be made without departing from the spirit of the invention. Accordingly, the invention is limited only by the following claims.

    __________________________________________________________________________     SEQUENCE LISTING     (1) GENERAL INFORMATION:     (iii) NUMBER OF SEQUENCES: 21     (2) INFORMATION FOR SEQ ID NO:1:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:     LysTrpLysSerPheIleLysLysLeuThrThrAlaValLysLysVal     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:2:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:     LysTrpLysSerPheIleLysLysLeuThrSerAlaAlaLysLysVal     151015     ValThrThrAlaLysProLeuIleSerSer     2025     (2) INFORMATION FOR SEQ ID NO:3:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:     LysTrpLysSerPheIleLysAsnLeuThrLysGlyGlySerLysIle     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:4:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:     LysTrpLysLysPheIleLysAsnLeuThrLysGlyGlySerLysIle     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:5:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:     LysTrpLysSerPheIleLysAsnLeuGluLysValLeuLysProGly     151015     GlyLeuLeuSerAsnIleValThrSerLeu     2025     (2) INFORMATION FOR SEQ ID NO:6:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:     LysTrpLysSerPheIleLysAsnLeuGluLysValLeuLysLysGly     151015     ProIleLeuAlaAsnLeuValSerIleVal     2025     (2) INFORMATION FOR SEQ ID NO:7:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4, 7, 8, 10, 11, 14, 15     (D) OTHER INFORMATION: where Xaa at positions 4, 7, 8, 10, 11,     14, or 15 is valine, leucine, isoleucine, phenylalanine,     tyrosine, tryptophan, methionine, alanine, cysteine,     glycine, proline or norleucine acid     (B) LOCATION: 5, 6, 9, 12, or 13     (D) OTHER INFORMATION: where Xaa at positions 5, 6, 9, 12, or     13 is serine, threonine, asparagine, glutamine, aspartic,     glutami, lysine, arginine or histidine acid     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:     LysTrpLysXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaVal     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:8:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4, 7, 8, 10, 11, 14, 15     (D) OTHER INFORMATION: where Xaa at positions 4, 7, 8, 10, 11,     14, or 15 is valine, leucine, isoleucine, phenylalanine,     tyrosine, tryptophan, methionine, alanine, cysteine,     glycine, proline or norleucine acid     (B) LOCATION: 5, 6, 9, 12, or 13     (D) OTHER INFORMATION: where Xaa at positions 5, 6, 9, 12, or     13 is serine, threonine, asparagine, glutamine, aspartic,     glutami, lysine, arginine or histidine acid     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:     LysTrpLysXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaVal     151015     ValThrThrAlaLysProLeuIleSerSer     2025     (2) INFORMATION FOR SEQ ID NO:9:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4, 7, 8, 10, 11, 14, 15     (D) OTHER INFORMATION: where Xaa at positions 4, 7, 8, 10, 11,     14, or 15 is valine, leucine, isoleucine, phenylalanine,     tyrosine, tryptophan, methionine, alanine, cysteine,     glycine, proline or norleucine acid     (B) LOCATION: 5, 6, 9, 12, or 13     (D) OTHER INFORMATION: where Xaa at positions 5, 6, 9, 12, or     13 is serine, threonine, asparagine, glutamine, aspartic,     glutami, lysine, arginine or histidine acid     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:     LysTrpLysXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaIle     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:10:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4, 7, 8, 10, 11, 14, 15     (D) OTHER INFORMATION: where Xaa at positions 4, 7, 8, 10, 11,     14, or 15 is valine, leucine, isoleucine, phenylalanine,     tyrosine, tryptophan, methionine, alanine, cysteine,     glycine, proline or norleucine acid     (B) LOCATION: 5, 6, 9, 12, or 13     (D) OTHER INFORMATION: where Xaa at positions 5, 6, 9, 12, or     13 is serine, threonine, asparagine, glutamine, aspartic,     glutami, lysine, arginine or histidine acid     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:     LysTrpLysXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaGly     151015     GlyLeuLeuSerAsnIleValThrSerLeu     2025     (2) INFORMATION FOR SEQ ID NO:11:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4, 7, 8, 10, 11, 14, 15     (D) OTHER INFORMATION: where Xaa at positions 4, 7, 8, 10, 11,     14, or 15 is valine, leucine, isoleucine, phenylalanine,     tyrosine, tryptophan, methionine, alanine, cysteine,     glycine, proline or norleucine acid     (B) LOCATION: 5, 6, 9, 12, or 13     (D) OTHER INFORMATION: where Xaa at positions 5, 6, 9, 12, or     13 is serine, threonine, asparagine, glutamine, aspartic,     glutami, lysine, arginine or histidine acid     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:     LysTrpLysXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaXaaGly     151015     ProIleLeuAlaAsnLeuValSerIleVal     2025     (2) INFORMATION FOR SEQ ID NO:12:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 4...4     (D) OTHER INFORMATION: where Xaa at position 4 is S, K, or E     (B) LOCATION: 8...8     (D) OTHER INFORMATION: where Xaa at position 8 is K, N, or E     (B) LOCATION: 10...10     (D) OTHER INFORMATION: where Xaa at position 10 is T, E, or Q     (B) LOCATION: 11...11     (D) OTHER INFORMATION: where Xaa at position 11 is K, T, S, or     (B) LOCATION: 12...12     (D) OTHER INFORMATION: where Xaa at position 12 is V, A, or G     (B) LOCATION: 13...13     (D) OTHER INFORMATION: where Xaa at position 13 is V, L, A, or     G     (B) LOCATION: 14...14     (D) OTHER INFORMATION: where Xaa at position 14 is K, S, or A     (B) LOCATION: 15...15     (D) OTHER INFORMATION: where Xaa at position 15 is K, or P     (B) LOCATION: 16...16     (D) OTHER INFORMATION: where Xaa at position 16 is V, G, or I     (B) LOCATION: 17...17     (D) OTHER INFORMATION: where Xaa at position 17 is L, V, G, or     P     (B) LOCATION: 18...18     (D) OTHER INFORMATION: where Xaa at position 18 is T, L, or I     (B) LOCATION: 19...19     (D) OTHER INFORMATION: where Xaa at position 19 is T, or L     (B) LOCATION: 20...20     (D) OTHER INFORMATION: where Xaa at position 20 is G, A, or S     (B) LOCATION: 21...21     (D) OTHER INFORMATION: where Xaa at position 21 is L, K, or N     (B) LOCATION: 22...22     (D) OTHER INFORMATION: where Xaa at position 22 is P, I, or L     (B) LOCATION: 23...23     (D) OTHER INFORMATION: where Xaa at position 23 is A, V, or L     (B) LOCATION: 24...24     (D) OTHER INFORMATION: where Xaa at position 24 is L, I, T, or     S     (B) LOCATION: 25...25     (D) OTHER INFORMATION: where Xaa at position 25 is I, or S     (B) LOCATION: 26...26     (D) OTHER INFORMATION: where Xaa at position 26 is S, L, or V     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12:     LysTrpLysXaaPheIleLysXaaLeuXaaXaaXaaXaaXaaXaaXaa     151015     XaaXaaXaaXaaXaaXaaXaaXaaXaaXaa     2025     (2) INFORMATION FOR SEQ ID NO:13:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (ix) FEATURE:     (B) LOCATION: 8...8     (D) OTHER INFORMATION: where Xaa at position 8 is K, or N     (B) LOCATION: 11...11     (D) OTHER INFORMATION: where Xaa at position 11 is K, or T     (B) LOCATION: 12...12     (D) OTHER INFORMATION: where Xaa at position 12 is V, A, or G     (B) LOCATION: 13...13     (D) OTHER INFORMATION: where Xaa at position 13 is V, or L     (B) LOCATION: 14...14     (D) OTHER INFORMATION: where Xaa at position 14 is K, or S     (B) LOCATION: 15...15     (D) OTHER INFORMATION: where Xaa at position 15 is K, or P     (B) LOCATION: 16...16     (D) OTHER INFORMATION: where Xaa at position 16 is V, or G     (B) LOCATION: 17...17     (D) OTHER INFORMATION: where Xaa at position 17 is L, V, or G     (B) LOCATION: 18...18     (D) OTHER INFORMATION: where Xaa at position 18 is T, or L     (B) LOCATION: 19...19     (D) OTHER INFORMATION: where Xaa at position 19 is T, or L     (B) LOCATION: 20...20     (D) OTHER INFORMATION: where Xaa at position 20 is G, A, or S     (B) LOCATION: 21...21     (D) OTHER INFORMATION: where Xaa at position 21 is L, K, or N     (B) LOCATION: 22...22     (D) OTHER INFORMATION: where Xaa at position 22 is P, I, or L     (B) LOCATION: 23...23     (D) OTHER INFORMATION: where Xaa at position 23 is A, V, or L     (B) LOCATION: 24...24     (D) OTHER INFORMATION: where Xaa at position 24 is L, or I     (B) LOCATION: 25...25     (D) OTHER INFORMATION: where Xaa at position 25 is I, or S     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13:     LysTrpLysSerPheIleLysXaaLeuThrXaaXaaXaaXaaXaaXaa     151015     XaaXaaXaaXaaXaaXaaXaaXaaXaaSer     2025     (2) INFORMATION FOR SEQ ID NO:14:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14:     LysTrpLysLeuPheLysLysIleGlyIleGlyAlaValLeuLysVal     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:15:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 28 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15:     LysTrpLysLeuPheLysLysIleGlyIleGlyAlaValLeuLysVal     151015     LeuThrThrGlyLeuProAlaLeuLysLeuThrLys     2025     (2) INFORMATION FOR SEQ ID NO:16:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:16:     LysTrpLysGluPheIleLysLysLeuThrThrAlaValLysLysVal     151015     LeuThrThrGlyLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:17:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:17:     LysTrpLysLysPheIleLysGluLeuGlnLysValLeuAlaProGly     151015     GlyLeuLeuSerAsnIleValThrSerLeu     2025     (2) INFORMATION FOR SEQ ID NO:18:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:18:     LysTrpLysSerPheIleLysLysLeuThrSerValLeuLysLysVal     151015     ValThrThrAlaLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:19:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:19:     LysTrpLysSerPheIleLysAsnLeuThrLysValLeuLysLysVal     151015     ValThrThrAlaLeuProAlaLeuIleSer     2025     (2) INFORMATION FOR SEQ ID NO:20:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:20:     LysTrpLysSerPheIleLysLysLeuThrSerValLeuLysLysVal     151015     ValThrThrAlaLysProLeuIleSerSer     2025     (2) INFORMATION FOR SEQ ID NO:21:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 26 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:21:     LysTrpLysLysPheIleLysGluLeuGlnLysValLeuLysProGly     151015     GlyLeuLeuSerAsnIleValThrSerLeu     2025     __________________________________________________________________________ 

We claim:
 1. An isolated antimicrobial peptide having an amino acid sequence selected from the group consisting of:NH₂ -KWKSFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:1), NH₂ -KWKSFIKKLTSAAKKVVTTAKPLISS-COOH (SEQ ID NO:2), NH₂ -KWKSFIKNLTKGGSKILTTGLPALIS-COOH (SEQ ID NO:3), NH₂ -KWKKFIKNLTKGGSKILTTGLPALIS-COOH (SEQ ID NO:4), NH₂ -KWKSFIKNLEKVLKPGGLLSNIVTSL-COOH (SEQ ID NO:5), NH₂ -KWKSFIKNLEKVLKKGPILANLVSIV-COOH (SEQ ID NO:6), NH₂ -KWK(S/K/E)FIK(K/N/E)L(TEQ)(K/T/S/G)(V/A/G)(V/L/A/G) (K/S/A)(K/P)(V/G/I)(L/V/G/P)(T/L/I)(T/L)(G/A/S)(L/K/N) (P/I/L)(ANV/L)(L/I/T/S)(I/S)(S/LNV)-COOH (SEQ ID NO:12), and NH₂ -KWKSFIK(K/N)LT(K/T)(V/A/G)(V/L)(K/S)(K/P)(V/G) (L/V/G)(T/L)(T/L)(G/A/S)(L/K/N)(P/I/L)(AV/L)(L/I) (I/S)S-COOH (SEQ ID NO:13).
 2. The peptide of claim 1, wherein the peptide has an amino acid sequence selected from the group consisting of:NH₂ -KWKEFIKKLTTAVKKVLTTGLPALIS-COOH (SEQ ID NO:16), NH₂ -KWKKFIKELQKVLAPGGLLSNIVTSL-COOH (SEQ ID NO:17), NH₂ -KWKSFIKKLTSVLKKVVTTALPALIS-COOH (SEQ ID NO:18), NH₂ -KWKSFIKNLTKVLKKVVTTALPALIS-COOH (SEQ ID NO:19), NH₂ -KWKSFIKKLTSVLKKVVTTAKPLISS-COOH (SEQ ID NO:20), and NH₂ -KWKKFIKELQKVLKPGGLLSNIVTSL-COOH (SEQ ID NO:21). 